1. Field of the Invention
The present invention relates to the field of insect repellents and insecticides. More particularly, the present invention is directed to processes for repelling and killing insects, compositions for repelling insects, compositions for killing insects, and the preferred use of a monoterpene, as well as other generally regarded as safe (GRAS) food additive materials, for the formulation of such compositions.
2. Description of the Prior Art
The control of insects, both for the protection of crops and animals, and for the maintenance of public health, has consumed much study and effort over the years. Ten percent of the food man produces is eaten by insects. Consequently, the control of insects to protect crops and livestock is of paramount importance, especially for farmers.
Insects are also especially commonplace in and around homes. Insects, such as flies, mosquitos, cockroaches and fleas ordinarily may function as vectors for contagious diseases.
Three main methods of chemically controlling insect pests are known and used; namely stomach poisons, contact poisons and fumigants. In the past, when there was less concern about the environment, little attention was paid to the toxicity of organic and inorganic materials employed to control insects. Today, virtually all the insect repellents and insecticides presently registered with the U.S. Environmental Protection Agency bear warnings prohibiting their use near food or in food-serving places and in waters bearing fish. Many of these insect control agents are toxic to humans if ingested, inhaled or physically contacted. There is a thus a demand for safer pesticides equal in efficacy to the more toxic ones presently available.
One area of interest in the production of environmentally safe insect repellents and insecticides is the use of Generally Regarded As Safe (GRAS) food flavorings. The monoterpene known as d-limonene is approved for use as a GRAS essential oil, food flavoring additive in foods eaten by humans (21 CFR, part 170-199, Food and Drugs, dated Apr. 1, 1990, incorporated herein by reference) and is similarly listed in the internationally recognized FOOD CHEMICALS CODEX (3d ed.) (incorporated herein by reference). This comparatively fast evaporating essential oil is derived from the peels of citrus fruit. Its fragrance has long been known to be a strong natural insect repellent and insecticide. In nature, for example, termites spray a naturally manufactured terpene at attacking ants to keep them at bay. Various terpenes, including d-limonene, are found in bark, and both repel and kill insects which attack living trees.
The natural repellency and insecticidal properties of d-limonene and its chemically related terpenes have been well documented for many years in scientific journals. More recently, in 1983, Dotolo, in U.S. Pat. No. 4,379,168, taught the limited use of d-limonene only as an insecticide and not as a repellent when mixed with surfactants, water, and a required antioxidant to keep the d-limonene from going rancid in the presence of air. However, the use of large volumes of water as specified in Dotolo's patent dilutes the efficacy of d-limonene.
The ability to repel animals, in general, and insects, in particular, may also be achieved by GRAS flavorings. U.S. Pat. No. 3,923,997 teaches the use of .alpha.-n-alkyl-.gamma.-butyrolactone and/or a .delta.-valerolactone as an anti-mating composition or as a repellent for animals.